1. Field of the Invention
The present invention relates to a method and an apparatus for processing image data based particularly on a bit map format.
2. Description of the Prior Art
There has been known heretofore that, when image data inclusive of video signals are processed after being once stored in a memory, an entire screen is divided into a plurality of blocks and the data are processed with regard to each of the divided blocks. Since the data processing is executed for the individual blocks, it becomes possible to reduce the amount of the data to be processed each time, hence minimizing the burden imposed on an image data processing circuit and so forth.
It is customary that, when various image data such as video signals are stored in the memory, data representative of color or the like is added to the image data for each of pixels constituting one screen, and the data of the entire pixels of one screen including the attributes of color data are stored in the memory. The data thus obtained by dividing one screen into component pixels is termed bit-map image data.
However, in such data processing for the divided screen blocks, there exists a disadvantage that the boundaries between the divided blocks are prone to conspicuous in the displayed image because of color differences. More specifically, when divided images are displayed in mutual proximity, there arises a problem that the display colors are rendered different from each other on both sides of the boundary between the divided blocks. And the boundary of such color tone variations is discerned as the boundary of the divided blocks.
In bit-map image data, color data and so forth are needed with regard to all pixels constituting one screen, so that the data required for one screen becomes great in amount to consequently increase the amount of the data processed by an image display circuit, hence raising a disadvantage of a great burden imposed on the processing circuit. More specifically, in the circuit for processing the image data to display the same, it is necessary to perform operations of first reading out the image data from a recording medium such as a disc or tape, then storing the image data once in a RAM included in the processing circuit and subsequently converting the data into video signals or the like to be displayed. However, the RAM incorporated in the processing circuit requires a great storage capacity to eventually enlarge the circuit scale.